Groundwater resource vulnerability and spatial variability of nitrate contamination: Insights from high density tubewell monitoring in a hard rock aquifer

Buvaneshwari, Sriramulu and Riotte, Jean and Sekhar, M and Kumar, M S Mohan and Sharma, Arnit Kumar and Duprey, Jean Louis and Audry, Stephane and Giriraja, P R and Praveenkumarreddy, Yerabham and Moger, Hemanth and Durand, Patrick and Braun, Jean-Jacques and Ruiz, Laurent (2017) Groundwater resource vulnerability and spatial variability of nitrate contamination: Insights from high density tubewell monitoring in a hard rock aquifer. In: SCIENCE OF THE TOTAL ENVIRONMENT, 579 . pp. 838-847.

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Abstract

Agriculture has been increasingly relying on groundwater irrigation for the last decades, leading to severe groundwater depletion and/or nitrate contamination. Understanding the links between nitrate concentration and groundwater resource is a prerequisite for assessing the sustainability of irrigated systems. The Berambadi catchment (ORE-BVET/Kabini Critical Zone Observatory) in Southern India is a typical example of intensive irrigated agriculture and then an ideal site to study the relative influences of land use, management practices and aquifer properties on NO3 spatial distribution in groundwater. The monitoring of >200 tube wells revealed nitrate concentrations from I to 360 mg/L. Three configurations of groundwater level and elevation gradient were identified: i) NO3 hot spots associated to deep groundwater levels (30-60.m) and low groundwater elevation gradient suggest small groundwater reserve with absence of lateral flow, then degradation of groundwater quality due to recycling through pumping and return flow; ii) high groundwater elevation gradient, moderate NO3 concentrations suggest that significant lateral flow prevented NO3 enrichment; iii) low NO3 concentrations, low groundwater elevation gradient and shallow groundwater indicate a large reserve. We propose that mapping groundwater level and gradient could be used to delineate zones vulnerable to agriculture intensification in catchments where groundwater from low-yielding aquifers is the only source of irrigation. Then, wells located in low groundwater elevation gradient zones are likely to be suitable for assessing the impacts of local agricultural systems, while wells located in zones with high elevation gradient would reflect the average groundwater quality of the catchment, and hence should be used for regional mapping of groundwater quality. Irrigatiori with NO3 concentrated groundwater induces a ``hidden'' input of nitrogen to the crop which can reach 200 kgN/ha/yr in hotspot areas, enhancing groundwater contamination. Such fluxes, once taken into account in fertilizer management, would allow optimizing fertilizer consumption and mitigate high nitrate concentrations in groundwater. (C) 2016 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	SCIENCE OF THE TOTAL ENVIRONMENT
Additional Information:	Copy right for this article belongs to the ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	28 Feb 2017 10:22
Last Modified:	11 Oct 2018 18:02
URI:	http://eprints.iisc.ac.in/id/eprint/56283

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